Troubleshooting Linux Time Synchronization with NTP

Time Synchronization The network time protocol helps computer systems to synchronize their time. We know this protocol by its shorter name NTP. In the past, it was not really a big issue if your system was a few minutes off. This changed with the interconnected world we are now living in. One of the better examples is networks relying on the authentication protocol Kerberos. If your system time is not correct, you may not be able to authenticate. This is because […]

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The Non-Technical Changelog: Insights of 6 Months Development

The Non-Technical Changelog Lessons learned between our last and current release The Lynis project team is proud to announce a new release of our security auditing tool. With months of work and a variety of changes, we bumped up the version to a “zero release” (2.2.0). The technical changelog is included in the download. We consider it to be a stable release, yet ask all to test it first. Being the original author of Lynis, there is an additional background […]

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Upgrading External Packages with unattended-upgrade

Upgrading External Packages with unattended-upgrade The unattended-upgrade tool is a great way to keep your system automatically updated. While you might not always want to do that for all packages, it definitely can be a great way to assist in your security efforts. In that case, tell it to track security updates and install the related packages. If you are using third-party packages (e.g. via PPAs), the system has no idea about security updates for those packages. So you need […]

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Find and Disable Insecure Services on Linux

Insecure Services on Linux The world has changed a lot in the last era, especially when it comes to computing. This applies also to the services we run on our Linux systems. Some of these services (like rlogin), were previously the defacto tools to do administration. Now they are considered to be bad and insecure. What makes a service insecure? Services can become insecure when they have characteristics like: No (or weak) authentication No (or weak) encryption Insecure protocols Running as […]

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Mosh, the SSH Alternative Option for System Administration

Reasons to use Mosh instead of SSH Mosh, or mobile shell, is the ideal tool for remote system administration. While SSH is great, Mosh beats it in several areas. Let’s dive into the reasons why it makes sense to learn about Mosh. Pros Session Resumption Remember the last time your connection was interrupted? It it frustrating and sometimes even leads to losing some of your work. The stable TCP connection is not always a blessing. Mosh comes to the rescue, especially […]

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Delete a HSTS Key Pin in Chrome

Delete a HSTS Key Pin in Chrome Key pinning can be tricky and sometimes you might encounter a website having an incorrect key pin. This is usually caused by renewing certificates. In that case the duration time of the key pin might overlap the expire time of the moment of renewal. Chrome Error You will be seeing an error something like: Your connection is not private   Attackers might be trying to steal your information from domain.com (for example, passwords, […]

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Automatic Security Updates with DNF

DNF: Automatic Security Updates The Dandified YUM tool, DNF, has become a powerful package manager for systems running Fedora. As it looks now, it will become also the default package manager for CentOS 8 and RHEL 8. One of the benefits from dnf is the option to retrieve security information very easily. This allows us to use it for automatic security patching of our Linux systems. Let’s explore the options and see how dnf-automatic can help us with fully automated […]

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Dealing with Linux Malware, Insights by the Author of rkhunter

Linux Malware Malicious software plague computers for more than 40 years. It is hard to think this threat will ever stop. The Linux platform definitely has their share of malware, although many people never experienced it firsthand. Let’s dive into this subject and discover why your system might actually being compromised at this very moment. The types of malware To understand the risks, you have to understand the threats and weaknesses. When we talk about malware, there are different family […]

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File Integrity of Password Files

Authentication Security Password files on Linux are used to store user details, like your unique user ID and name. It defines who you are on the system, your access to files, and the permissions you have. Proper password management, together with file integrity of your password files, is important. It keeps your system and user accounts safe.   Password Files For most Linux distributions there are two related files available: /etc/passwd and /etc/shadow. The first file defines what local users […]

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Deleting Outdated HPKP Key Pins in Firefox

HPKP Key Pins in Firefox HPKP is a great technology to pin a certificate to a website. On first use of a domain, the browser of the client checks if key pinning is available. Upon a next visit, the browser applies an additional check if the certificate(s) provided is available in the previous list of white-listed sites. HPKP error Sometimes things go wrong with HPKP and you won’t be able to access a particular page. The best action is first to […]

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Showing Available Security Updates with DNF

Checking Security Updates for your Software Packages DNF is the default package manager since Fedora 22. As it is considered to be a better version of YUM, some of our Lynis users asked for DNF support. With focus on auditing and security patching, we definitely wanted to see that for ourselves. While building support, I’ve gathered the most important commands. In this blog post we will have a look how we can leverage the DNF output to show only the […]

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File permissions of the /etc/shadow password file

Linux password files and permissions The password files are an important cornerstone of the security of your Linux system. Commonly they are /etc/passwd and /etc/shadow, and installed by default. Sometimes we receive questions what the right permissions of these files should be. Therefore this blog post to have a look at the file permissions (and ownership) of both files. Passwd file The password file stores local accounts of the system. It is a readable text file and uses colons (:) […]

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Differences between iptables and nftables explained

The seasoned Linux administrator will be familiar with iptables, the network traffic filter. If you ever configured a Linux system with an ethernet bridge configuration, you might even have worked with ebtables. Or possibly you wanted to filter ARP traffic and used arptables? Newcomer nftables has arrived, with the purpose to replace iptables, ip6tables, ebtables and arptables. As with every big upcoming change, it is good to know the differences. We explain what makes nftables different to iptables, and why […]

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Linux Security Guide for Hardening IPv6

Linux Security Guide for Hardening IPv6 Version 6 of Internet Protocol is now 20+ years available. You would think it is widely available now, right? Not exactly. Still many internet providers don’t have it deployed for their customers. Hosting companies are not always eager to deploy it either. Mostly because of lacking knowledge. To get at east more knowledge shared on the security side of IPv6, we have crafted this guide. Hopefully it will be a practical guide for your […]

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How to see the file type?

Did you come across a file, but don’t know what type it is? Let’s learn how to analyze it. The unknown file You may encounter a file on your system with known contents or goal. Usually, the first thing we do is then use cat to show the contents, or execute it. While that makes sense, it may be dangerous to do. It might be a piece of malware, disrupt your screen output or even hang the terminal. Here is […]

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